Building automation systems (BAS) are used to coordinate, manage, and automate control of diverse environmental, physical, and electrical building subsystems, particularly HVAC and climate control but also including security, lighting, power, and the like. Typical existing BAS systems are hardwired or use a proprietary communication standard or protocol to link the various subsystems and provide system-wide user access, monitoring, and control.
A BAS can comprise a plurality of end devices, a communication network, a server engine, and a graphical user interface (GUI) or other means of providing control and reporting data to a user. The end devices are each typically associated with a room, a space, a system, or a subsystem for at least a portion of a building or a campus. The communication network may support a plurality of communication protocols and communicatively couples end devices to the server engine. Examples of the types of data that these systems collect about the space, building or system can include pressures, temperatures, humidity level, power/energy readings, and other run-time statistics.
Hardwiring and manual programming of BAS systems can create a robust fixed system customized for a particular installation. These systems, however, often require extensive customization for each building or site. Particular manual programming and other installation elements may not be applicable to other systems, contributing to the costliness and time-consuming installation associated with such systems.
Further, hardwired systems and those using proprietary communication standards and protocols are difficult or impossible to integrate with system components, devices, panels, and other elements from different vendors or generations. For example, a campus of buildings in which an upgraded BAS is being installed may have existing previous generation (legacy) systems and systems from more than one vendor. Installing a BAS and making it compatible with the existing systems in such a situation is time-consuming, requiring extensive manual service and programming to integrate the existing devices and implement the custom BAS.
With the introduction of BACnet™, an ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and ANSI (American National Standards Institute) protocol standard, and LonTalk™, a protocol integration approach developed by Echelon, some uniformity of standards and communications has been achieved in the industry. BACnet™ was intended to standardize HVAC interoperability and serve as a solution to industry-wide issues. In use, however, BACnet™ exists in multiple versions and includes various non-standard feature functions available to vendors.
One aspect of many BACnet™ compatible devices is the passive handling of communicating their condition of operation or on-line/off-line status. For example a device may transition from being on-line to off-line without actively notifying any other devices or even a system controller of the change in the device's status. For these types of devices the only method of detecting off-line conditions is for the system controller or other management engine to actively query or poll each individual device for its current status.
Those skilled in the art of network traffic management will recognize that the frequent or periodic polling of a large number of individual devices may lead to network performance degradation. Additionally, in the area of BAS management some devices may be battery operated or capable of only a limited data communication rate or processing capacity. Because of these potential conditions the use of a polling or periodic “heartbeat” method of gathering the state of every device in a BAS system may not be effective or desirable. For these and other reasons, a need remains for an intelligent BAS having the capability of actively managing the state of BACnet™ compatible devices and other proprietary devices that do not broadcast their change in status.